package com.changanw.uppermoststring;

import java.util.HashSet;
import java.util.Set;

public class LongestSubstring {
    public static int lengthOfLongestSubstring(String s) {
        // 哈希集合，记录每个字符是否出现过
        Set<Character> occ = new HashSet<Character>();
        int n = s.length();
        // 右指针，初始值为 -1，相当于我们在字符串的左边界的左侧，还没有开始移动
        int rk = -1, ans = 0;
        for (int i = 0; i < n; ++i) {
            if (i != 0) {
                // 左指针向右移动一格，移除一个字符
                occ.remove(s.charAt(i - 1));
            }
            while (rk + 1 < n && !occ.contains(s.charAt(rk + 1))) {
                // 不断地移动右指针
                occ.add(s.charAt(rk + 1));
                ++rk;
            }
            // 第 i 到 rk 个字符是一个极长的无重复字符子串
            ans = Math.max(ans, rk - i + 1);
        }
        return ans;

    }
    public static int longSubstring(String s){
        int length = s.length();
        int ans = 0;
        Set<Character> characterSet = new HashSet<>();
        for (int i = 0; i < length; i++) {
            characterSet.add(s.charAt(i));
            for (int j = i+1;j <= length;j++){
                if (j == length || characterSet.contains(s.charAt(j))){
                    ans = Math.max(ans,j-i);
                    characterSet.clear();
                    break;
                }else {
                    characterSet.add(s.charAt(j));
                }
            }

        }


        return ans;
    }

    public static void main(String[] args) {
        String s = "abcc";
        final int i = LongestSubstring.lengthOfLongestSubstring(s);
        //final int i1 = LongestSubstring.longSubstring(s);
        System.out.println(i);


    }
}
